U.S. patent application number 15/951663 was filed with the patent office on 2018-10-18 for system and method for power conversion.
The applicant listed for this patent is Accion Systems, Inc.. Invention is credited to Paul E. Fogel.
Application Number | 20180301998 15/951663 |
Document ID | / |
Family ID | 63790325 |
Filed Date | 2018-10-18 |
United States Patent
Application |
20180301998 |
Kind Code |
A1 |
Fogel; Paul E. |
October 18, 2018 |
SYSTEM AND METHOD FOR POWER CONVERSION
Abstract
A polarity-selectable high voltage direct current power supply
including a first drive assembly that transforms a first low
voltage DC input into a first medium voltage alternating current
output; a first HV output assembly that transforms the first LV AC
output into a first HV DC output, wherein the first HV output
assembly defines a first input stage; a polarity selector coupled
between the second output junction of the first drive assembly and
the first and second input stages of the first HV output assembly,
the polarity selector operable between a first configuration and a
second configuration; wherein in the first configuration the first
HV DC output has a positive polarity; and wherein in the second
configuration the first HV DC output has a negative polarity.
Inventors: |
Fogel; Paul E.; (Boston,
MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Accion Systems, Inc. |
Boston |
MA |
US |
|
|
Family ID: |
63790325 |
Appl. No.: |
15/951663 |
Filed: |
April 12, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62484705 |
Apr 12, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02M 1/08 20130101; H02M
3/3376 20130101; H02M 3/33569 20130101; H02M 2001/008 20130101;
H02M 3/33561 20130101; H01J 27/022 20130101; H02M 7/103
20130101 |
International
Class: |
H02M 3/335 20060101
H02M003/335; H02M 1/08 20060101 H02M001/08; H01J 27/02 20060101
H01J027/02 |
Goverment Interests
STATEMENT OF FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT
[0002] This invention was made with government support under
15-C-0176 awarded by the Department of Defense. The government has
certain rights in the invention.
Claims
1. A polarity-selectable high voltage (HV) direct current (DC)
power supply comprising: a first drive assembly that transforms a
first low voltage (LV) DC input into a first medium voltage (MV)
alternating current (AC) output, wherein the first drive assembly
defines a first output junction and a second output junction; a
first HV output assembly that transforms the first LV AC output
into a first HV DC output, wherein the first HV output assembly
defines a first input stage directly electrically connected to the
first output junction, a second input stage directly electrically
connected to the first output junction, and a first HV DC output
junction; a polarity selector coupled between the second output
junction of the first drive assembly and the first and second input
stages of the first HV output assembly, the polarity selector
comprising a set of switches operable between a first configuration
and a second configuration; wherein in the first configuration: the
set of switches directly electrically connects the second output
junction to the first input stage and electrically isolates the
second output junction from the second input stage, and the first
HV DC output has a positive polarity; and wherein in the second
configuration: the set of switches directly electrically connects
the second output junction to the second input stage and
electrically isolates the second output junction from the first
input stage, and the first HV DC output has a negative
polarity.
2. The system of claim 1, wherein the first drive assembly
comprises: an inverter electrically coupled between the first LV DC
input and an LV reference potential, wherein the inverter
transforms the LV DC input into a LV AC output, and a step-up
transformer comprising an input coil coupled to the inverter and an
output coil coupled to the first and second output junction,
wherein the step-up transformer transforms the LV AC output into
the MV AC output.
3. The system of claim 2, wherein the inverter comprises a
full-bridge inverter.
4. The system of claim 2, wherein the first HV output assembly
comprises a voltage ladder comprising a set of intermediate
voltage-doubling stages coupled between the first input stage and
the HV output junction and coupled between the second input stage
and the HV output junction.
5. The system of claim 1, further comprising a controller
communicatively coupled to the HV output junction and the polarity
selector, wherein the controller receives a feedback signal
proportional to a magnitude of the first HV DC output and operates
the polarity sector between the first configuration and the second
configuration based on the feedback signal.
6. The system of claim 5, further comprising a feedback isolator
directly electrically coupled to the HV output junction and the
controller, wherein the feedback isolator receives a first sense
signal referenced to an HV reference potential and generates the
feedback signal based on the first sense signal, wherein the
feedback signal is referenced to an LV reference potential.
7. The system of claim 5, further comprising a load coupled between
the first HV DC output and an HV reference potential, wherein the
load comprises an ion emitter that emits anions when the polarity
selector is in the first configuration and cations when the
polarity selector is in the second configuration.
8. The system of claim 5, further comprising: a second drive
assembly that transforms the first LV DC input into a second MV AC
output, wherein the second drive assembly defines a third output
junction and a fourth output junction; a second HV output assembly
that transforms the second LV AC output into a second HV DC output,
wherein the second HV output assembly defines a third input stage
directly electrically connected to the third output junction, a
fourth input stage directly electrically connected to the third
output junction, and a second HV DC output junction; wherein the
set of switches of the polarity selector is operable between a
third configuration and a fourth configuration; wherein in the
third configuration: the set of switches directly electrically
connects the fourth output junction to the third input stage and
electrically isolates the fourth output junction from the fourth
input stage, and the second HV DC output has a positive polarity;
and wherein in the fourth configuration: the set of switches
directly electrically connects the fourth output junction to the
fourth input stage and electrically isolates the fourth output
junction from the third input stage, and the second HV DC output
has a negative polarity.
9. The system of claim 8, wherein the set of switches comprises a
set of double-pole double-throw switches, and in the first
configuration the polarity selector is simultaneously in the fourth
configuration, and in the second configuration the polarity
selector is simultaneously in the third configuration.
10. The system of claim 9, further comprising: a first load coupled
between the first HV DC output and an HV reference potential,
wherein the first load comprises an ion emitter that emits anions
when the polarity selector is in the first configuration and emits
cations when the polarity selector is in the second configuration;
and a second load coupled between the second HV DC output and the
HV reference potential, wherein the second load comprises an ion
emitter that emits cations when the polarity selector is in the
fourth configuration and emits anions when the polarity selector is
in the third configuration.
10. system of claim 10, further comprising: a feedback isolator
directly electrically coupled to the first HV output junction, the
second HV output junction, and the controller, wherein the feedback
isolator receives a first sense signal from the first HV output
junction referenced to an HV reference potential and a second sense
signal from the second HV output junction referenced to the HV
reference potential, and generates the feedback signal based on the
first sense signal and the second sense signal, wherein the
feedback signal is referenced to an LV reference potential; and a
crowbar switch operable between a first mode and a second mode by
the controller, wherein in the first mode the crowbar switch
directly electrically connects the HV reference potential and the
LV reference potential, and wherein in the second mode the crowbar
switch electrically isolates the HV reference potential and the LV
reference potential.
12. A method for supplying polarity-selectable high voltage (HV)
power, comprising: at a power supply, transforming a first low
voltage (LV) direct current (DC) input into a first HV DC output
defining an output polarity relative to an HV reference potential,
wherein the output polarity is one of a first polarity and a second
polarity opposite the first polarity, wherein transforming
comprises: converting the first LV DC input into a first LV
alternating current (AC) output at an inverter of the power supply,
converting the first LV AC output into a first medium voltage (MV)
AC output at a step-up transformer of the power supply, and
converting the first MV AC output into the first HV DC output at a
power rectifier of the power supply; powering a first ion emitter
with the first HV DC output, wherein the first ion emitter emits
ions having an ion polarity equal to the output polarity;
measuring, at a controller of the power supply, a first operating
parameter of the first ion emitter; and using the controller,
actuating a polarity selector of the power supply based on the
first operating parameter simultaneously with powering the first
ion emitter, wherein the polarity selector is arranged between the
step-up transformer and the power rectifier of the power supply,
and wherein actuating the polarity selector switches the output
polarity between the first polarity and the second polarity.
13. The method of claim 12, wherein the first operating parameter
comprises an ion current emitted by the first ion emitter, and
further comprising actuating the polarity selector at an actuation
frequency defining a period, wherein the actuation frequency is
determined by the controller to maintain a net sum of the ion
current over the period substantially equal to zero.
14. The method of claim 12, wherein the first operating parameter
comprises an accumulated charge imbalance associated with the first
ion emitter, and further comprising: switching the first polarity
based on the accumulated charge imbalance exceeding a threshold
value.
15. The method of claim 12, further comprising: at the power
supply, transforming the first LV DC input into a second HV DC
output defining a second output polarity relative to the HV
reference potential, wherein the second output polarity is one of
the first polarity and the second polarity; powering a second ion
emitter with the second HV DC output, wherein the second ion
emitter emits ions having a second ion polarity equal to the second
output polarity; measuring, at the controller of the power supply,
a second operating parameter of the second ion emitter; and wherein
actuating the polarity selector switches the second output polarity
between the first polarity and the second polarity.
16. The method of claim 15, wherein actuating the polarity selector
comprises maintaining the first output polarity and the second
output polarity as opposing polarities, and wherein a first ion
current drawn by the first ion emitter is substantially equal to
and opposite in polarity to a second ion current drawn by the
second ion emitter.
17. The method of claim 15, wherein the first ion emitter draws a
first ion current, wherein the second ion emitter draws a second
ion current, and further comprising controlling, at the controller,
a first magnitude of the first HV DC output and a second magnitude
of the second HV DC output such that the first ion current is
greater than the second ion current.
18. The method of claim 12, further comprising: receiving, at a
feedback isolator of the power supply, a first sense signal
referenced to the HV reference potential; generating, at the
feedback isolator, a first feedback signal referenced to an LV
reference potential; and controlling a setpoint of the first HV DC
output based on the first feedback signal.
19. The method of claim 18, wherein the feedback isolator and the
controller comprise an analog electrical circuit.
20. The method of claim 18, further comprising connecting the LV
reference potential to the HV reference potential such that a
potential difference between the HV reference potential and the LV
reference potential is substantially equal to zero.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application Ser. No. 62/484,705, filed 12 Apr. 2017, which is
incorporated herein in its entirety by this reference.
TECHNICAL FIELD
[0003] This invention relates generally to the power processing
field, and more specifically to a new and useful variable polarity
controllable power supply system in the power processing field.
BRIEF DESCRIPTION OF THE FIGURES
[0004] FIG. 1 is a schematic representation of a variation of the
system.
[0005] FIG. 2 is a schematic representation of a variation of the
system with a full-bridge inverter.
[0006] FIG. 3 is a schematic illustration of a crowbar switch of a
variation of the system.
[0007] FIG. 4 is a schematic representation of an example
full-bridge inverter of the system.
[0008] FIG. 5 is a schematic representation of an example
half-bridge inverter of the system.
[0009] FIGS. 6A-B are schematic representations of voltage
amplification stages of a portion of a variation of the system.
[0010] FIG. 7 is a flowchart of data and/or power flows in a
variation of the system and example implementation of a variation
of the method.
[0011] FIG. 8 is a flowchart of data and/or power flows in a
variation of a portion of the system and example implementation of
a portion of the method.
[0012] FIG. 9 is a schematic representation of polarity-selectable
input stages of a portion of a variation of the system.
[0013] FIG. 10 is a flowchart of an example implementation of the
method.
[0014] FIG. 11 is a flowchart of a portion of an example
implementation of the method.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] The following description of the preferred embodiments of
the invention is not intended to limit the invention to these
preferred embodiments, but rather to enable any person skilled in
the art to make and use this invention.
1. Overview
[0016] As shown in FIG. 1, the system 100 includes: a drive
assembly 110, an output assembly 120, and a polarity selector 130
coupled between the drive assembly 110 and the output assembly 120.
The system 100 can also include: a controller 140, a feedback
isolator 150, a housing 160, a power source 170, one or more loads
180, and any other suitable components for powering ion sources
and/or generating ions.
[0017] The system 100 functions to provide polarity-switchable
output power to one or more loads 180. The system can also function
to provide feedback-controlled output power. The system can also
function to provide high-voltage (HV) output power. The system can
also function to provide direct current (DC) output. The system can
also function to: convert low voltage (LV) power to HV power;
mitigate (e.g., negate) accumulated charge imbalance, such as in
cases wherein net input and/or output currents have an
unpredictable or varying polarity; power one or more ion emitters
(e.g., ion thrusters, ion sources, etc.); provide power for thrust
generation for a spacecraft; generate thrust; provide power for
ion-based processing tools (e.g., ion mills, semiconductor
fabrication tools, etc.); and have any other suitable function
related powering ion sources and/or generating ions.
[0018] As shown in FIG. 10, the method 200 includes: transforming a
LV DC input into an HV DC output defining an output polarity S210;
powering a load with the HV DC output S220; measuring an operating
parameter of the load S230; and actuating a polarity selector 130
to switch the output polarity of the HV DC output based on the
operating parameter S240. The method 200 can additionally or
alternatively include: controlling a setpoint of the HV DC output
S222; generating an isolated feedback signal S232; and connecting
two or more reference potentials S234.
[0019] The method 200 functions to provide polarity switchable
power to one or more loads 180. The method 200 can also function to
provide feedback-controlled output power. The method 200 can also
function to provide HV output power, DC output power, and any other
suitable output power. The method 200 can also function to:
mitigate (e.g., negate) accumulated charge imbalance, such as in
cases wherein net input and/or output currents have an
unpredictable or varying polarity; power one or more ion emitters
(e.g., ion thrusters, ion sources, etc.); provide power for thrust
generation for a spacecraft, provide power for ion-based processing
tools (e.g., ion mills, semiconductor fabrication tools, etc.), and
have any other suitable function related to high voltage power
provision.
2. Benefits
[0020] Variants of the technology can confer several benefits
and/or advantages. First, variants can reduce wear on system
components (e.g., loads, high-voltage active electrostatically
charged components) while enabling efficient high-voltage operation
(e.g., operation at high voltage for longer time than using other
power sources) by allowing the polarity to be switched. For
example, in cases wherein the load performance degrades over time
while being powered by an output having a first polarity (e.g., due
to a decrease in ion extraction efficiency, electrospray
efficiency, etc.), switching the polarity of the power applied to
the load can reset load performance to a baseline level (e.g., the
performance level prior to the degradation due to continuous
operation in a first polarity mode).
[0021] Second, variants of the technology can reduce the weight of
weight-constrained vehicles (e.g., spacecraft, aircraft) by
reducing the weight and/or number of components of the power
supply, because M (e.g., any integer number M) output assemblies
can be controlled using a single isolated feedback loop (e.g.,
instead of using M feedback-enabled output assemblies with M sets
of feedback-related components).
[0022] Third, variants of the technology can enable provision of
feedback-controlled, equal-current-magnitude, opposite-polarity
high voltage power to an even number of loads (e.g., two
electrostatic ion accelerators, four ion sources, etc.) to generate
equal power dissipation (e.g., in generating thrust, in generating
surface-treating ion beams, etc.) without accumulated charge
imbalance (e.g., an increase of the magnitude of net charge of the
system from which the ions are emitted).
[0023] Fourth, variants of the technology can siphon charge buildup
(e.g., mitigate a buildup of space charge) from loads that build up
static charge of unpredictable and/or varying polarity (e.g.,
aircraft in flight, vehicles moving through the air and isolated
from a charge source/sink, etc.).
[0024] Fifth, variants of the technology can enable the application
of switchable-polarity high-voltage electric fields to the outputs
of electrostatic precipitators in order to extract charged and/or
polarizable particulates from fluid streams (e.g., to extract and
thereby reduce emitted pollutants and particulates).
[0025] Sixth, variants of the technology including
adjustable-voltage outputs can enable ion implantation (e.g., for
ions having similar charge per ion) at varying depths via
electrostatic acceleration, and/or at similar depths (e.g., for
ions having varying charge per ion).
[0026] Seventh, variants of the technology can provide a robust
power supply and/or thrust system that can withstand the rigors of
a space environment (e.g., thermal stress, radiation stress, etc.)
as well as a launch environment (e.g., acoustic stress, vibration,
etc.).
[0027] Eighth, variants of the technology can provide dual
opposite-polarity outputs that cooperatively define a virtual
ground (e.g., a floating center potential), such that other
components of the system and related components can be electrically
referenced to the virtual ground.
[0028] Ninth, variants of the technology can enable thrust
vectoring using ion thrusters. The ion thrusters can be inherently
charge-balanced (e.g., produce a net space charge of zero at the
spacecraft, draw a net ion current of zero from the power supply,
achieve charge neutrality in the overall ion output, etc.), or can
be intentionally operated to produce or negate a net charge on the
spacecraft (e.g., to negate an existing space charge, to
intentionally produce a net space charge, etc.). For example, a
first thruster and a second thruster can be arranged to produce a
net torque on the spacecraft, while the first and second thruster
draw equal and opposite ion currents. In another example, the first
and second thruster can be arranged such that a net torque is
produced on the spacecraft only when the ion currents drawn by each
thruster are dissimilar (e.g., wherein ion current and thrust are
directly proportional).
[0029] Tenth, variants of the technology can enable purely analog
control of a balanced bipolar power supply. For example, an analog
electrical circuit can be used to implement isolated analog
feedback control of the output power. In another example, an analog
electrical circuit can be used to implement analog feedback control
without electrical isolation of the feedback signals from sense
signals (e.g., output signals from input signals of the feedback
controller 140). In these examples and related examples, analog
control circuits can include networks of operational amplifiers and
passive components arranged in any suitable manner. The analog
control circuits can be manufactured as integrated circuits (e.g.,
system on chip, on a single chip, etc.), as printed circuit boards
with integrated circuits and other components attached thereto,
and/or as any suitable combination of the aforementioned integrated
circuits and printed circuit boards, or in any other suitable
manner of construction.
[0030] However, variants of the technology can additionally or
alternatively provide any other suitable benefits and/or
advantages.
3. System
[0031] As shown in FIG. 1, the system 100 includes: a drive
assembly 110, an output assembly 120, and a polarity selector 130
coupled between the drive assembly 110 and the output assembly 120.
The system 100 can also include: a controller 140, a feedback
isolator 150, a housing 160, a power source 170, a plurality of
drive assemblies, a plurality of output assemblies, one or more
loads 180, and any other suitable components for powering ion
sources and/or generating ions. The system is preferably capable of
performing the method disclosed below, but can alternatively or
additionally perform any other suitable method.
[0032] In variations, the system can include a plurality of drive
assemblies and/or a plurality of output assemblies, mutually
coupled in various ways. For example, the system can include
multiple drive assemblies having a one-to-one correspondence with
multiple output assemblies, each of the multiple drive and output
assemblies connected to and controlled by a single controller 140
and a single feedback isolator 150; however, there can be any other
suitable correspondence between controller 140(s), feedback
isolator(s), and one or more output and drive assemblies (e.g., two
controller 140s connected to and controlling two pairs of
output/drive assemblies, each controller 140 and each output
assembly 120 connected to a single feedback isolator 150).
[0033] Components of the system are preferably radiation-hardened
(e.g., operable in a space environment exposed to solar radiation,
gamma-ray burst radiation, Van Allen radiation, etc.) but can
alternatively be non-radiation hardened. Components of the system
are also preferably adapted for any other thermal and physical
stresses common to the space environment, such as rapid thermal
cycling, radiative cooling, micrometeorite impacts, and the like;
however, in alternative variations, the components can be adapted
for operation in other environments imposing different thermal and
physical stresses.
[0034] Variants of the system can be operable between several
modes. In some variations, the system is operable in a bipolar
output mode (e.g., two output assemblies are operated to generate
equal and opposite high voltage outputs by the controller 140,
which receives feedback from the feedback isolator 150, which
receives sense signal inputs from the output of each output
assembly 120). In some variations, the system is operable in a
single output mode (e.g., a single output assembly 120 is operated
to produce either a positive or negative polarity output, which is
switchable and/or controllable during operation without cessation
of power provision). In other variations, the system is selectively
operable between the bipolar output mode (multiple output modes)
and the single output mode (e.g., based on operation instructions,
output feedback, etc.). In alternative variations, the system can
be configured to operate any suitable number of output assemblies
at any suitable output voltage and output polarity.
[0035] The system can be used with (or include) one or more of the
following related systems, subsystems, or components (e.g., as
loads, as input power sources, etc.): a charged-particle (e.g.,
ion) thruster (e.g., an ionic colloid thruster, electrospray
thruster, etc.), which can include an electrostatic emitter array
and an extractor grid; an ionic particle-removal fluid filter;
and/or any other suitable system. The extractor grid of an ionic
colloid thruster can be used in conjunction with one or more
variants of the system by operating the grid at a high voltage
(e.g., an extraction potential, 500 volts, 1 kilovolt, etc.)
relative to the emitter, which can cause polarized droplets to form
at the tip of each electrostatic emitter and to be expelled axially
through and past the grid, creating thrust in the opposite
direction. Droplets formed from the ionic liquid (e.g., conductive
liquid, colloid) have a net charge, and the expulsion of the
droplets can lead to charging of the system utilizing the thruster
(e.g., spacecraft, aircraft, watercraft, etc.) unless equal and
opposite charge is also removed from the system. Accordingly, such
a thruster is preferably operated using multiple emitter arrays,
with emitter-extractor potential differences energized to achieve
equal and opposite extraction currents (e.g., with extractor grids
charged at equal and opposite-polarity extraction potentials) to
generate and accelerate ions, wherein the total net charge of the
system after ion-expulsion is at or near zero (e.g., as near to
zero as possible in order to prevent system charging). Such a
thruster can additionally or alternatively be operated using a
single-polarity array, wherein the charging polarity is
periodically switched (e.g., from positive to negative, negative to
positive) to mitigate space-charge buildup of the system (e.g.,
operated for equal time duration in each polarity mode to produce
net-zero charge on the system after an even number of positive and
negative-polarity operation periods). An ion thruster or
electrospray thruster can additionally or alternatively be operated
using the power processing system in any other suitable manner,
including without switching the charging polarity. Variants of the
power processing system as described herein can provide the
features for operating ion thrusters in the manner described above,
as well as any other suitable systems in any other suitable
manner.
[0036] The system and components thereof can include circuits and
sub-circuits, some or all of which can include ground connections.
Such ground connections can include connections to Earth-ground,
chassis ground, a battery terminal, a signal ground, a low voltage
(LV) reference potential, an HV reference potential, and/or any
other suitable reference potential. The system can include
electrical connections to and between active and passive
components. Each component in a serial connection can define an
"upstream" connection point and a "downstream" connection point,
wherein the upstream connection point is considered to be the point
at which current flowing in the conventional current direction
would enter the component if a positive polarity voltage difference
were generated or produced across the component, and wherein the
downstream connection point is considered to be the point at which
conventionally flowing current would exit the component if a
positive polarity voltage difference were placed across the
component. For diodes and other nominally polarity-dependent or
polarity-sensitive components, the upstream connection point is
defined relative to the direction that current can pass through the
component during normal operation (e.g., operation in the designed
direction for the diode or similar polarity-dependent circuit
component). Any of the system components and circuits can define
junctions at which the components are coupled together (e.g., an
input junction, an output junction, a pair of input junctions, a
pair of output junctions, etc.), and/or where switches associated
with various components (e.g., the polarity selector 130, the load
coupler 124, etc.) alternately connect and/or disconnect components
(e.g., selective thrusters, etc.) and circuits from one
another.
3.1 Drive Assembly
[0037] The drive assembly 110 functions to convert input power
(e.g., low voltage DC battery power) into a waveform suitable for
rectification into the HV DC output. Accordingly, the waveform
output by the drive assembly 110 is preferably a medium voltage
(MV) alternating current (AC) waveform, wherein the peak-to-peak
voltage is greater than a peak-to-peak voltage of the input signal
but less than the voltage of the HV DC output. However, the drive
assembly 110 can additionally or alternatively output any suitable
waveform. The drive assembly 110 is preferably coupled between an
input power source 170 and the polarity selector 130, such that
operation of the drive assembly 110 is unchanged regardless of the
output polarity of the output assembly 120 (e.g., determined by the
state of the polarity selector 130). However, the drive assembly
110 can be otherwise suitably coupled to other system components.
The drive assembly 110 can include an inverter 112 and a
transformer 114.
[0038] The system can include a plurality of drive assemblies. In a
variation, each drive assembly 110 of the plurality of drive
assemblies can be associated with a respective output assembly 120,
and separated therefrom by a single polarity selector 130 (e.g.,
wherein the single polarity selector 130 simultaneously determines
the output polarity of each of the output assemblies using the
switches of the polarity selector 132) or multiple polarity
selector 130s (e.g., wherein a plurality of polarity selector 130s
independently select the output polarities of the output
assemblies). In specific example, the system includes a pair of
drive assemblies coupled to a pair of output assemblies by a single
polarity selector 130, and the output polarities of the pair of
output assemblies are maintained in opposition by the polarity
selector 130 (e.g., wherein the HV DC output of the first output
assembly 120 is positive while the HV DC output of the second
output assembly 120 is negative and vice versa). However,
variations of the system including a plurality of drive assemblies
can include any other suitable arrangements thereof.
[0039] The inverter 112 of the drive assembly 110 functions to
convert the input power to an AC waveform (e.g., an LV AC output).
The inverter 112 includes a set of switches, each of which is
connected to the gate driver 146 by a signal pathway (e.g., an
electrical pathway, a trace, etc.). The inverter 112 is also
connected to the input power source 170, which is preferably a low
voltage DC source (e.g., a battery, a photovoltaic panel, a 10 V
source, 40 V source, 100 V source, or any other suitable voltage
source). The output AC waveform of the inverter 112 is preferably a
square wave (e.g., equal duty cycle square wave, unequal duty cycle
square wave, etc.) that alternates between the positive or negative
input voltage and ground. Alternatively, the output waveform can
alternate between 0 V and the input voltage (V.sub.in), between
+/-V.sub.in/2, or any other suitable voltages less than or equal to
V.sub.in. In further alternatives, the output waveform can be any
suitable AC waveform (e.g., sinusoidal, a discrete approximation of
a sine wave, asymmetric duty cycle square wave, saw wave,
etc.).
[0040] The switches of the inverter function to selectively open
and close portions of the inverter circuit to convert the low
voltage DC input power to an AC output waveform (e.g., invert the
input power). Each switch includes a control input (e.g., gate
connection) that is connected to the gate driver 146 by a signal
pathway. The gate driver 146 preferably controls (e.g., actuates)
the switch to change state (e.g., change between an open and closed
state, change between a closed and open state) to conductively
connect (or disconnect) an upstream side of the switch with a
downstream side of the switch. The switches can be any suitable
type of switch (e.g., N-type or P-type transistors, MOSFETs, FETs,
high speed solid-state relays, silicon-controlled rectifiers, or
any other suitable switch).
[0041] As shown in FIGS. 2 and 4, a first specific example of the
inverter 112 is a full-bridge inverter 112 that includes four
switches. In this example, the upstream side of the first switch is
connected to the input power and the upstream side of the second
switch. The downstream side of the first switch is connected to the
high side (e.g., the side closest to the input power connection in
the circuit between the input power and ground) of the transformer
primary winding and the upstream side of the third switch. The
upstream side of the second switch is connected to the input power
and the upstream side of the first switch. The downstream side of
the second switch is connected to the low side (e.g., the side
farthest from the input power connection in the circuit between the
input power and ground) of the primary winding of the transformer
114 and the upstream side of the fourth switch. The upstream side
of the third switch is connected to the high side of the
transformer primary winding and the downstream side of the first
switch. The downstream side of the third switch is connected to
ground and the downstream side of the fourth switch. The upstream
side of the fourth switch is connected to the low side of the
transformer primary winding and the downstream side of the second
switch. The downstream side of the fourth switch is connected to
the downstream side of the third switch and ground. Each switch has
a gate connection that is connected to the gate driver 146 of the
controller 140.
[0042] As shown in FIG. 5, a second specific example of the
inverter 112 is a half-bridge inverter that includes two switches.
The input power is connected to a center tap of the transformer
primary winding. The upstream side of the first switch is connected
to a first side of the transformer primary winding. The downstream
side of the first switch is connected to ground and to the
downstream side of the second switch. The upstream side of the
second switch is connected to a second side of the transformer
primary winding. The downstream side of the second switch is
connected to ground and the downstream side of the first switch.
Both switches have a gate connection that is connected to the gate
driver 146 of the controller 140.
[0043] The transformer 114 of the drive assembly 110 functions to
increase the voltage of the LV AC output of the inverter 112 to a
medium voltage (MV) AC output. The transformer 114 includes a
primary side and a secondary side, which are preferably a primary
winding and a secondary winding but can alternatively take any
suitable form. The windings can be made of any conductive material
(e.g., copper) and can optionally include a ferrous core.
Alternatively, the transformer 114 can be a ceramic
piezo-transduction transformer, or any other suitable step-up
transformer 114. The transformer 114 is preferably connected at the
primary side to the inverter, and at the secondary side to the
power rectifier 122 (preferably by way of the polarity selector 130
of the controller 140, but alternatively directly connected or
otherwise suitably connected). The transformer 114 can be
center-tapped (e.g., input power is connected at a center turn of
the primary winding and the inverter 112 is connected at each end
of the winding) or end-tapped (e.g., input power and ground are
switchably connected to each end of the primary winding), or
otherwise tapped in any suitable manner.
[0044] In a specific example of the drive assembly 110, the drive
assembly 110 includes an inverter 112 and a step-up transformer
114. The inverter 112 is electrically coupled between a source of
input power (e.g., an LV DC input) and a reference potential (e.g.,
a reference junction, a ground plane, etc.). The inverter 112 in
this example transforms the input power (e.g., an LV DC input) into
an output suitable for voltage increase by the transformer 114
(e.g., into a LV AC output). In this example, the inverter 112 is
coupled to an input coil of the step-up transformer 114 which
transforms the output received from the inverter 112 (e.g., the LV
AC output) into a higher voltage alternating current output (e.g.,
an MV AC output).
[0045] However, the output assembly 120 can be otherwise
configured, arranged, and/or used.
3.2 Output Assembly
[0046] The output assembly 120 functions to convert the output of
the drive assembly 110 (e.g., a medium voltage AC waveform) into a
high voltage direct current output defining an output polarity. The
output polarity of the output assembly 120 is switchable by way of
the polarity selector 130. The output assembly 120 includes a power
rectifier 122. The output assembly 120 can also include a load
coupler 124 and a sense signal rectifier 126. The output assembly
120 can also function to selectively couple and decouple a load to
and from the output HV DC power, respectively, by way of the load
coupler 124. The output assembly 120 can also function to produce a
sense signal proportional to an operating parameter of the output
power (e.g., and/or the load), such as the output voltage, output
current, load voltage drop, load current, and any other suitable
operating parameter, by way of the sense signal rectifier 126.
[0047] The power rectifier 122 of the output assembly 120 functions
to convert the medium voltage AC waveform to a high voltage DC
output. The power rectifier 122 can additionally function to
provide polarity-selectable (e.g., via the polarity selector 130 of
the controller 140) and magnitude-controllable (e.g., via a
variable tap output) output voltage to a load. The power rectifier
122 can additionally function to multiply the magnitude of the
input voltage in producing the output voltage (e.g., amplify the
voltage, step-up the voltage). The system preferably includes a
single power rectifier 122 per output assembly 120, but can
alternatively include any suitable number of power rectifiers
(e.g., cascaded/serial power rectifiers, parallel power rectifiers,
or any combination thereof). The power rectifier 122 preferably
includes one or more voltage doubling stages, and can optionally
include a half-doubling stage and a variable-tap output;
additionally or alternatively, the power rectifier 122 can include
any suitable components for rectification. In a first variation,
the power rectifier 122 includes an N-stage (e.g., 3 stage, 5
stage, 50 stage) voltage doubling ladder (e.g., with a maximum
output voltage of 2N times the peak output voltage of the
transformer secondary side) with a selectable (e.g., variable) tap
output, that can be selectively connected (e.g., by the controller
140 in cooperation with a multi-position selectable switch) to a
node between any two stages of the ladder, enabling any even
integer multiple of the voltage input to the ladder to be obtained
at the output. The power rectifier 122 preferably has a positive
polarity input and a negative polarity input, each of which can be
selectively coupled (e.g., by the polarity selector 130) to the
secondary side of the transformer 114 to enable polarity-selectable
output voltage at the output of the power rectifier; however, the
power rectifier 122 can have any other suitable inputs, selectable
or otherwise.
[0048] The voltage doubling stage of the power rectifier 122
functions to provide double the output voltage (e.g., relative to
ground) as the voltage input to the stage. In a specific example,
the voltage doubling stage includes two diodes and two capacitors.
As shown in FIG. 6A, the upstream side of the first capacitor is
connected to the input of the stage; the downstream side of the
first capacitor is connected to the downstream side of the first
diode and the upstream side of the second diode; the upstream side
of the first diode is connected to ground and the upstream side of
the second capacitor; and the downstream side of the second diode
is connected to the downstream side of the second capacitor and the
output of the stage. Any number of voltage doubling stages can be
placed in series, wherein the output of the stage is the input to
the next sequential stage, to achieve a 2N factor increase in the
initial input voltage (i.e., where N is the number of stages).
[0049] The power rectifier 122 can optionally include a
half-doubling stage, which functions to enable odd-integer voltage
level multiplication, when used in combination with a voltage
doubling stage. In a specific example, the half-doubling stage
includes a third capacitor and a third diode (in addition to the
two capacitors and two diodes of a voltage doubling stage). As
shown in FIG. 6B, the upstream side of the third diode is connected
to the input to the stage and the upstream side of the first
capacitor; the downstream side of the third diode is connected to
the downstream side of the third capacitor, the upstream side of
the first diode, and the upstream side of the second capacitor; and
the upstream side of the third capacitor is connected to a ground
connection (or other suitable reference potential). There is
preferably a single half-doubling stage in sequence with the set of
N voltage doubling stages, but there can alternatively be multiple
half-doubling stages connected in any suitable manner, and/or
half-doubling stages may be omitted in alternative variations of
the power rectifier 122.
[0050] The power rectifier 122 can optionally include a
variable-tap output, which functions to allow the output voltage of
the power rectifier 122 to be selected from the available node
voltages of the N-stage voltage ladder (e.g., by adjusting which
two stages the upstream side of the output connection is
electrically connected to). For example, the power rectifier 122
can include a multiposition switch (e.g., a rotary switch,
transistor network, relay network, etc.) that is controllable by
the controller 140 to connect the output of the power rectifier 122
to any connection between any two stages of the N-stage voltage
ladder of the power rectifier 122.
[0051] The load coupler 124 of the output assembly 120 functions to
electrically connect the load to the power output (e.g., junction)
of the power rectifier 122. The load coupler 124 can be a permanent
coupler (e.g., a solder joint, a permanent connector, etc.), a
controllable (e.g., switchable) coupler (e.g., a switch, a relay, a
controllable spark gap switch, an arc switch, etc.), and any other
suitable coupler. In variations of the output assembly 120
including a load coupler 124, the load coupler 124 can be
controlled (e.g., by the controller 140) in addition to and/or as
an alternative to switching the output polarity (e.g., to cease
powering the load instead of and/or in addition to switching the
output polarity of the output assembly 120 coupled to the
load).
[0052] The sense signal rectifier 126 of the output assembly 120
functions to rectify the signal detected at the output of the power
rectifier 122 in order to provide a sense signal (e.g., to a
feedback isolator 150) that does not depend on the polarity of the
output of the power rectifier 122. The signal rectifier 126 can
additionally function to electrically isolate the output of the
power rectifier 122 (e.g., the voltage sense input) from the
controller 140 and/or other portions of the system. In a specific
example, as shown in FIG. 2, the signal rectifier 126 includes a
first shunt resistor, connected between the power rectifier output
and the inputs of two parallel, oppositely-directed diodes, each
diode connected to ground across a second and third shunt resistor,
respectively. A negative sense output is connected between the
second shunt resistor and the voltage sense input 152 of the
feedback isolator 150, and a positive sense output is connected
between the third shunt resistor and the voltage sense input 152 of
the feedback isolator 150. Accordingly, a positive voltage sense
input 152 is received at the feedback isolator 150 regardless of
the output polarity of the power rectifier 122.
[0053] However, the output assembly 120 can be otherwise
configured, arranged, and/or used.
3.3 Polarity Selector 130
[0054] The polarity selector 130 functions to select the output
polarity of the output assembly 120 (e.g., the output polarity of
the HV DC output of the output assembly 120). The polarity selector
130 is preferably controlled by the controller 140 (e.g., based on
an output control signal generated by the controller 140), but can
be otherwise suitably controlled. The polarity selector 130 is
preferably electrically connected (e.g., permanently connected,
selectively connectable by a switch, etc.) between the drive
assembly 110 and the output assembly 120, but can be otherwise
connected.
[0055] In an example configuration, as shown in FIG. 9, the
polarity selector 130 can include a pair of single-pole,
single-throw (SPST) relays that connect the secondary winding of
the transformer 114 between ground and either the positive or
negative polarity inputs of the power rectifier, respectively, and
each SPST is either in a closed or open state based on the output
polarity control signal. In related examples, the polarity selector
130 can include two or more SPST relays or one or more single-pole,
double throw (SPDT) relays in a latching configuration. However,
the polarity selector 130 can include any suitable switches for
redirecting the output of the secondary winding of the transformer
114 (e.g., solid state relays, MOSFETs, BJT transistors, etc.).
[0056] In another example configuration, the polarity selector 130
includes a double pole, double-throw (DPDT) relay that is arranged
between the secondary windings of two transformers, each
transformer 114 associated with a different drive assembly 110, and
the input stages of two output assemblies (e.g., one throw of the
relay is coupled between each drive assembly 110 and output
assembly 120). In this example, when the DPDT relay is in a first
of two switch positions, the first output assembly 120 defines a
positive output polarity and the second output assembly 120 defines
a negative output polarity, and when the DPDT relay is in a second
of two switch positions, the first output assembly 120 defines a
negative output polarity and the second output assembly 120 defines
a positive output polarity. Thus, with a single control signal
operating the DPDT relay, the output polarity of a pair of output
assemblies can be switched back and forth while the output
polarities remain in opposition (e.g., one negative and one
positive output).
[0057] In another example configuration, the polarity selector 130
is coupled between one of two output junctions of the drive
assembly no and the positive and negative input stages 123 of the
output assembly 120. In this example, the polarity selector 130
includes a set of switches operable between a first configuration
and a second configuration. In the first configuration, the set of
switches directly electrically connects the output junction to the
positive input stage and electrically isolates the output junction
from the negative input stage, such that the output polarity of the
output assembly 120 is positive. In the second configuration, the
set of switches directly electrically connects the output junction
to the negative input stage and electrically isolates the output
junction from the positive input stage, such that the output
polarity of the output assembly 120 is negative. In this example
configuration, a load connected downstream of the output assembly
120 can remain connected and operational during polarity selection,
such as in cases wherein the load can perform a function
irrespective of the polarity of its input power (e.g., wherein the
load is an ion accelerator that can accelerate both positive and
negative ions from the same propellant source).
[0058] However, the polarity selector 130 can be otherwise
configured and/or connected to the system components.
3.4 Controller
[0059] The controller 140 functions to set the output voltage,
current, and polarity of the output assembly 120. The controller
140 can additionally function to receive external commands (e.g.,
manually or automatically generated by a ground control system or
team, automatically generated by a command module of a spacecraft).
The controller 140 can additionally function to provide operational
data (e.g., state information regarding the system, real time
performance and/or power consumption of the system and/or loads
thereof, the output current and/or voltage transmitted to a load,
etc.) to other related systems (e.g., a spacecraft computer,
command module, a ground control system, a flight computer, etc.).
The controller 140 is communicatively coupled to (and controls) the
inverter 112 of the output assembly 120, the feedback isolator 150,
and to the secondary side of the transformer 114 of the output
assembly 120. The controller 140 is preferably coupled to the
inverter 112 by direct electrical connections (e.g., wires, traces)
but can be otherwise coupled. The system preferably includes a
single controller 140, but can alternatively include any number of
controllers. The system preferably includes a single controller 140
per output assembly 120, but can alternatively include a single
controller 140 per pair of two output assemblies or any other
suitable ratio of controllers to output assemblies and/or other
components of the system. The controller 140 preferably includes a
microcontroller 142, a first combiner 144, a second combiner 145,
and a gate driver 146, but can include any other suitable
component. The controller 140 can optionally include a PWM
controller 148, as well as any other suitable controller (e.g., a
field-programmable gate array/FPGA, an analog feedback controller,
etc.).
[0060] The controller 140 can optionally include a PWM controller
148, which can function to control the gate driver 146 based on
combined command signals received from the first and second
combiners. The PWM controller 148 can also function to directly
control switches of the inverter (e.g., bypassing the gate driver
in cases wherein a gate driver is omitted from the system or in
cases wherein the gate driver is included and is bypassed for any
suitable reason), and/or to control any other suitable switches of
the system. The PWM controller 148 can additionally function to
control the gate driver 146 based on the operating mode of the
system (e.g., current-controlled mode, voltage-controlled mode),
which can correspond to different output waveforms of the PWM
controller 148 (e.g., fixed frequency and variable duty cycle
square-wave output in voltage-controlled mode, fixed duty cycle and
variable frequency square-wave output in current-controlled mode,
etc.). In a first variation, the PWM controller 148 outputs a
control signal to the gate driver 146 with a signal characteristic
(e.g., RMS magnitude, frequency) that is selected in response to
variation of the current feedback signal away from a current set
point (e.g., desired output current magnitude); in a second
variation, the control signal characteristic is selected in
response to variation of the voltage feedback signal away from a
voltage set point (e.g., desired output voltage). In both these
variations and related variations, the output of the PWM controller
148 is determined based on (e.g., in response to, in direct
relation to) the combined voltage and/or current command signals
received from the first and/or second combiners (e.g., the output
is feedback-controlled). However, the output of the PWM controller
148 can be otherwise determined.
[0061] The controller 140 can be operable between several modes.
The controller 140 can be operated in a direct PWM mode, wherein
the microcontroller 142 provides PWM control signals directly to
the gate driver 146 (e.g., without feedback and without a PWM
controller 148); alternatively, the controller 140 can include the
PWM controller 148 and the PWM controller 148 provides PWM control
signals (e.g., generated based on feedback) to the gate driver 146.
The controller 140 can be operated in positive (or negative) output
polarity mode, wherein the controller 140 selectively completes a
circuit (e.g., using a SPST relay, or any other suitable relay or
switch) between the secondary side (e.g., output) of the
transformer 114 and the positive (or negative) polarity input of
the power rectifier, which results in current flow through the
power rectifier 122 such that the output potential of the power
rectifier 122 is positive (or negative). In one variation, the
controller 140 preferably provides 2*M polarity control signals to
2*M single-pole single-throw (SPST) relays, where M is the number
of output assemblies controlled by the controller 140. However, the
controller 140 can alternatively provide M polarity control signals
to M dual-pole single-throw (DPST) relays, or provide any other
suitable number of polarity control signals. The controller 140 can
be operable in feedback control mode (e.g., voltage controlled,
current controlled), wherein the microcontroller 142 provides a
voltage command signal to the first combiner 144, which receives M
voltage feedback signals from the feedback isolator 150 and
generates and provides a combined voltage command signal to the PWM
controller 148. The microcontroller 142 also generates and provides
a current command signal to the second combiner 145, which receives
a current feedback signal from the feedback isolator 150 and
generates and provides a combined current command signal to the PWM
controller 148. In a related variation, the feedback control mode
can include receiving feedback signals bypassing an isolated
amplifier (e.g., bypassing the feedback isolator), such as directly
from a sense output of a transformer (e.g., a third winding within
the transformer that outputs a voltage sense signal proportional to
the output of the step-up winding), an output of another component
(e.g., the high voltage output assembly, a sense output of the HV
output assembly, etc.), and from any other suitable location and/or
junction in the system. The PWM controller 148 preferably provides
control signals to M gate drivers based on the combined current
and/or voltage command signals (e.g., when operated in
current-controlled mode and/or voltage-controlled mode), but can
alternatively provide control signals to any number of gate
drivers. Each gate driver 146 generates P drive signals, wherein P
is equal to the number of switches in the inverter 112 (e.g., P=4
for a full bridge inverter, P=2 for a half bridge inverter), and
provides the P drive signals to the gate terminals of the switches
(e.g., MOSFETs) of the inverter 112 according to the control
signals received from the PWM controller 148. In variations, each
gate driver 146 can alternatively generate a single drive signal
(e.g., wherein P=1). Each of the signals described above (e.g.,
control signals, command signals, feedback signals) can be analog
or digital, at any suitable voltage level (e.g., TLL voltage, 3.3
volts, etc.), and can correspond to any suitable data transfer
protocol or format (e.g., binary logic levels, I2C, modulated
waveform, etc.). Signals are preferably transmitted over direct
electrical connections (e.g., wires, conductive pathways, traces)
but can alternatively be otherwise transmitted (e.g., wirelessly,
such as through inductive coupling).
[0062] The microcontroller 142 functions to generate control
outputs, and to transmit control outputs to other components of the
system. The microcontroller 142 can additionally function to
receive external instructions, execute preprogrammed instructions,
or any combination thereof. The microcontroller 142 can be
implemented in hardware in various ways, such as in a CPU, an ASIC,
an FPGA, an embedded controller chipset, and in any other suitable
hardware implementation. The microcontroller 142 is preferably
electrically connected to each output assembly 120 by one positive
and negative output control pair, to the first combiner 144 by a
signal pathway, and to the second combiner 145 by a signal pathway.
However, the microcontroller 142 can be otherwise connected. The
microcontroller 142 can optionally be directly connected to the
gate driver 146 (e.g., for operation in direct PWM control mode) by
a signal pathway, and/or optionally directly connected to any
suitable switch (e.g., a switch of the inverter, a switch of the
polarity selector, a digital-input MOSFET, a BJT, etc.).
[0063] The first combiner 144 functions to combine voltage feedback
signals and the voltage control command signal to generate the
combined voltage command signal, and to provide the combined
voltage command signal to the PWM controller 148. As such, the
first combiner 144 is connected to the feedback isolator 150 by a
number of signal pathways equal to the number of voltage feedback
signals (e.g., one per output assembly 120) and to the
microcontroller 142 by a signal pathway (e.g., over which the
voltage command signal is transmitted). In a specific example, the
first combiner 144 includes: a first summing junction at which a
first voltage feedback signal is summed with an inverted voltage
command signal to generate a first residual signal; a second
summing junction at which a second voltage feedback signal is
summed with the inverted voltage command signal to generate a
second residual signal; a comparator junction connected to the
outputs of the two summing junctions at which the residual signal
(e.g., error signal) with the greatest magnitude is selected and
provided as an output (e.g., the combined voltage command signal)
to the PWM controller 148. In related examples, the first combiner
144 can include an averaging junction (e.g., wherein a number of
feedback signals are received and averaged instead of and/or in
addition to summed), in addition to and/or in lieu of a summing
junction, wherein signals are averaged to generate an output signal
(e.g., an output feedback signal).
[0064] The second combiner 145 functions to combine the current
feedback signal and the current command signal to generate the
combined current command signal, and to provide the combined
current command signal to the PWM controller 148. As such, the
second combiner 145 is connected to the feedback isolator 150 by a
signal pathway and to the microcontroller 142 by a signal pathway
(e.g., over which the current command signal is transmitted). In a
specific example, the second combiner 145 includes: a summing
junction at which the current feedback signal is summed with an
inverted current command signal to generate a residual signal which
is provided as an output (e.g., the combined current command
signal) to the PWM controller 148.
[0065] The gate driver 146 functions to control and power (e.g.,
drive) the inverter 112 (e.g., the switches of the inverter) of the
drive assembly 110. The gate driver 146 integrated into the
controller 140 (e.g., connected to a PWM controller 148 of the
controller, connected to a microcontroller 142 of the controller,
etc.) by one or more signal pathways, and to the inverter 112 by a
number of signal pathways corresponding to the number of switches
of the inverter. There is preferably a single gate driver 146 per
inverter, but can additionally or alternatively be any suitable
number of gate drivers associated with any suitable number of
inverters (e.g., a single gate driver 146 per switch of each
inverter, a single gate driver 146 for all switches of multiple
inverters, etc.). The gate driver 146 preferably outputs PWM
square-wave signals at a voltage level and current capacity at
which the switches of the inverter 112 are designed to operate
(e.g., according to manufacturer specifications, 3.3 volts peak to
peak, 5 volts peak to peak, etc.) but can alternatively output any
suitable drive signals at any suitable power levels. The output
characteristics (e.g., voltage level, current level, pulse widths,
pulse frequency, etc.) are preferably determined by the PWM
controller 148, but can alternatively be determined by the
microcontroller 142 or otherwise suitably determined. Drive signals
are preferably carried over signal pathways connecting the gate
driver 146 and the inverter 112 (e.g., switches of the inverter),
but can be otherwise carried or transmitted. Each drive signal is
preferably carried over a single signal pathway, but alternatively
multiple drive signals may be multiplexed over a single signal
pathway and/or a branched signal pathway; however, drive signals
can be otherwise suitably carried. The gate driver 146 preferably
outputs a number of drive signals equal to the number of switches
of the inverter 112 (e.g., two drive signals for an inverter 112
including a half-bridge, four drive signals for an inverter 112
including a full-bridge), but can alternatively output any suitable
number of drive signals associated with any suitable number of
switches.
[0066] In a specific example, the controller 140 is communicatively
coupled to an output junction of the output assembly 120 (e.g., an
HV output junction) and to the polarity selector 130. In this
example, during operation, the controller receives a feedback
signal proportional to the magnitude (e.g., voltage magnitude,
current magnitude, etc.) of the HV DC output of the output assembly
120, and operates the polarity sector based on the feedback signal
(e.g., to select the output polarity of the output assembly 120).
Operating the polarity selector 130 based on the feedback signal
can include: switching the polarity based on the magnitude of the
output falling below a threshold value (e.g., an ion current
threshold indicative of decreasing load performance); maintaining
the output polarity based on the magnitude of the output falling
within a threshold range (e.g., a nominal voltage range indicative
of operation within an acceptable deviation from the set point);
and otherwise suitably operating the polarity selector 130.
[0067] However, the controller 140 can be otherwise configured,
arranged, and/or used.
3.5 Feedback Isolator
[0068] The feedback isolator 150 of the system functions to convert
feedback of either positive or negative polarity that originates
from the output assembly 120 into feedback of a single polarity,
for provision to the controller 140 as a feedback input. The single
polarity is preferably positive polarity, but can alternatively be
negative. The feedback output by the feedback isolator 150 is
preferably referenced to a different reference potential than the
signals received by the feedback isolator 150 (e.g., sense signals
received from the output assembly 120), but can be referenced to
the same reference potential as the feedback isolator 150, the
reference potential for the drive assembly 110, the reference
potential for the polarity selector 130, or to any other suitable
reference potential. The feedback isolator 150 includes a signal
rectifier 126, one or more voltage sense inputs 152, one or more
current sense inputs 154, a current feedback output 158, and one or
more voltage feedback outputs 156. The system preferably includes a
single feedback isolator 150, even for cases in which there are
multiple output assemblies, but there can alternatively be any
suitable number of feedback isolators. The feedback isolator 150 is
connected to sensor outputs of the secondary side of each
transformer 114 (e.g., to sense the output current) and to sensor
outputs at the output of each power rectifier 122 (e.g., to sense
the output voltage) by signal pathways, as well as to the
controller 140 by one or more signal pathways (e.g., for
transmitting feedback signals); additionally or alternatively, the
feedback isolator 150 can be otherwise connected to components of
the system in order to receive and/or transmit signals (e.g.,
feedback signals).
[0069] The voltage sense inputs 152 of the feedback isolator 150
function to receive the voltage sensor signals from the sense
signal rectifier 126 of the output assembly 120, and thus are
preferably connected via signal pathways to the signal rectifier
126. However, the voltage sense inputs 152 can be otherwise
connected.
[0070] The current sense inputs 154 of the feedback isolator 150
function to receive the current sense signal from the output
assembly 120 (e.g., the secondary side of the transformer). In a
first specific example, the current sense signal is generated by a
voltage across a shunt resistor connected between the low side of
the transformer secondary winding and ground, and the current sense
input 154 receives the current sense signal as a double-ended
voltage signal across the shunt resistor. However, the current
sense signal can be otherwise generated (e.g., at the high voltage
output, at a third winding of a transformer, etc.).
[0071] The feedback outputs (e.g., current feedback outputs,
voltage feedback outputs) of the feedback isolator 150 function to
provide feedback signals to the first and second combiners of the
controller 140. The system preferably includes M voltage feedback
outputs 156, where M is the number of output assemblies connected
to the feedback isolator 150, but the system can alternatively
include any suitable number of voltage feedback outputs 156
connected to the first combiner 144. The system preferably includes
a single current feedback output 158 (e.g., for use in controlling
a single input power source), but there can alternatively be any
suitable number of current feedback outputs 158 connected to the
second combiner.
[0072] In some variants, the system can include a crowbar switch
159 that functions to connect one or more reference potentials used
in various components of the system. In an example, the crowbar
switch 159 is operable between a first mode and a second mode by
the controller 140, wherein in the first mode the crowbar switch
159 directly electrically connects the HV reference potential
(e.g., the reference potential to which the output power of the
output assembly 120 is referenced) and the LV reference potential
(e.g., the reference potential to which outputs of the controller
140 and/or feedback isolator 150 are referenced, a signal ground
plane reference, etc.), and wherein in the second mode the crowbar
switch 159 electrically isolates the HV reference potential and the
LV reference potential. This variation can be used to selectively
switch the system from an analog or passive charge-balancing mode
to a digital or active charge-balancing mode, wherein the
controller 140 can actively control charge balancing (e.g., by
computing and controlling the drive assemblies based on output
feedback). Additionally or alternatively, this variation can be
used to monitor the load health. For example, the crowbar switch
159 can be operated in the second mode, wherein the current drawn
by the load can be monitored and used to determine whether the load
is operational (e.g., considered operational when the current
exceeds a threshold value, and considered nonoperational when the
current falls below the threshold value). The crowbar switch 159
can include various types of switches, such as: a relay, a latch, a
solenoid-controlled gap, a transistor, a thyratron, and any other
suitable switch for connecting two electrical conductors to remove
the potential difference between the two conductors. In additional
or alternative variations, the crowbar switch 159 can include a
network of switches, which can function to connect and/or
disconnect multiple isolated references (e.g., two or more
reference potentials) in any suitable manner (e.g., wherein a
subset of reference potentials are equalized via crowbar switch
connection and a distinct subset remain isolated, wherein all
reference potentials are equalized, etc.).
3.6 Power Source
[0073] The system can optionally include a power source 170, which
functions to provide input power to the inverter 112 for subsequent
upconversion to high voltage by the transformer 114 and power
rectifier 122. The power source 170 can additionally function to
power the controller 140 (e.g., including DC-DC regulation of the
power source 170 to appropriate power levels for the controller
140). The system preferably includes a single power source 170, but
there can alternatively be multiple (e.g., each connected to the
same inverter 112 and/or controller 140 permanently, or
controllably by a switch; alternatively they may be connected to
different inverters and/or controllers, permanently or controllably
by switches). In a first variation, the power source 170 is a
rectified DC voltage from an AC source (e.g., an alternator). In a
second variation, the power source 170 is a regulated DC source
(e.g., a battery, a DC voltage regulator). In a third variation,
the power source 170 is a fluctuating and/or uncontrolled DC source
(e.g., an unconditioned or partially-conditioned solar panel
output). In a fourth variation, the power source 170 is an AC
source (e.g., in variations of the system without an inverter, in
variations of the system with an additional rectification stage
between the power source 170 and the inverter) such as wall power,
an alternator, or any other suitable AC source.
3.7 Housing
[0074] The system can optionally include a housing 160, which
functions to enclose and shield at least a portion of the power
processing system. The housing 160 can additionally function to
define throughputs (e.g., feedthroughs) for power transmission
lines to pass into and out of the housing 160 and connect to
various sources and/or loads 180. The housing 160 can additionally
function to define throughputs (e.g., feedthroughs) for control
and/or data transmission lines to pass into and out of the housing
160 and connect to various components of the system. The housing
160 can additionally function to passively transport heat (e.g.,
among components, away from components, toward components, etc.).
For example, the housing 160 can define heat conduction elements
and/or support elements configured to conduct heat away from
portions of electronic components dissipating electrical energy as
heat toward other regions of the system (e.g., to the external
surface of the housing such that it radiates away, to components
that are colder than their optimal temperature operating range,
etc.). However, the housing 160 can additionally or alternatively
transport thermal energy in any suitable manner, by way of any
suitable elements and/or defined morphological features.
[0075] The housing 160 is preferably configured to provide
structural support to and an enclosure for components of the power
processing system, but can alternatively be otherwise configured.
The housing 160 preferably has a form factor configured for
integration into a standard satellite bus (e.g., a 1U cubesat, a 3U
cubesat, a nanosatellite, a kilowatt-class telecom satellite,
etc.), but can additionally or alternatively have any suitable form
factor. As such, the housing 160 can include the flanges, bolt
patterns, physical layouts, standoffs, and any other suitable
features that conform to standards and/or regulations regarding
spacecraft integration. The housing 160 preferably provides
shielding against solar and other space radiation (e.g., through
the use of a radiation-hardened material casing, a specified wall
thickness, etc.), but in variations can alternatively provide
minimal radiation shielding.
3.8 Loads
[0076] The system can optionally include a primary load 182, which
functions to receive and dissipate the output power of the power
rectifier 122. The primary load 182 is electrically connected to
the output of the output assembly 120 (e.g., the selected
variable-tap output of the N-stage voltage doubler of the power
rectifier) between the high voltage output and ground. The system
preferably includes a single primary load 182 per output assembly
120, but can additionally or alternatively include multiple primary
loads 182 per output assembly 120, multiple output assemblies
connected to a single primary load 182, or any other suitable
correspondence between any number of primary loads and any number
of output assemblies. The primary load 182 can, in variations, have
an operating voltage limit (e.g., a breakdown voltage, a voltage
above which operational efficiency drops below a threshold), which
can, in variations, be less than the maximum output voltage of the
output assembly 120. The operating voltage limit can be prescribed
and static in time, but can alternatively change with time (e.g.,
as components wear). There is preferably a single primary load 182
per output assembly 120, but there can alternatively be any
suitable number of primary loads connected to an output assembly
120 (e.g., via a multiplexer between the output assembly 120 and a
plurality of primary loads).
[0077] In a first specific example, the primary load 182 includes
an ion source. The ion source includes a body (e.g., an emitter
body) that includes a base and a tip. The body can be made of a
porous material (e.g., a microfabricated emitter body formed from a
porous metal substrate) compatible with an ionic liquid or a room
temperature molten salt (e.g., does not react or result in
electrochemical decaying or corrosion). The body can be mounted
relative to a source of ionic liquid or a source of a room
temperature molten salt. The body can include a pore size gradient
that decreases from the base of the body to the tip of the body,
such that ionic liquid can be transported through capillarity
(e.g., through capillary forces) from the base to the tip; however,
ionic liquid can additionally or alternatively be transported
through capillarity without a pore size gradient or by any other
suitable transport mechanism. The ionic liquid can be continuously
transported through capillarity from the base to the tip so that
the ion source (e.g., emitter) avoids liquid starvation. An
electrode can be positioned downstream relative to the body. The
output assembly 120 of the power processing unit can apply high
voltage to the body relative to the electrode, thereby emitting a
current (e.g., a beam of ions) from the tip of the body. The
application of a voltage can cause emission of ions from the tip
(e.g., via formation of a Taylor cone at the tip). In a related
example, the ion source can include a plurality of emitters in a 1D
or 2D array, wherein each emitter is microfabricated substantially
as described above. The emitters of the array can have an emitter
spacing of less than about 1 mm, or any other suitable spacing; the
spacing between emitters may limit the maximum voltage that can be
applied due to field-enhancement effects generated at the emitter
tips (however, the spacing between emitters may alternatively have
no effect on the applicable maximum voltage).
[0078] The system can optionally include a secondary load 184,
which functions to receive and dissipate voltage(s) produced by the
power processing system that are greater than the voltage applied
to the primary load 182. In a first variation, the primary load 182
is connected to the output assembly 120 and receives an output
voltage selected by the controller 140 (e.g., using a variable-tap
output) that is less than the maximum output voltage of the output
assembly 120 (e.g., the primary load is powered at 100*V.sub.in
wherein the output assembly 120 can produce 300*V.sub.in); the
secondary load 184 can then be connected to the output assembly 120
at a secondary output connection that provides the maximum output
voltage (e.g., 300*V.sub.in). In a specific example, the secondary
load 184 includes an acceleration electrode (e.g., a grid
electrode) positioned downstream of an extractor electrode of an
ion source as described above, wherein the extractor electrode is
the primary load 182. Thus, additional momentum can be transferred
to the ions as they are accelerated downstream of the primary load
182 without increasing the applied voltage at the primary load 182
(e.g., by way of staged acceleration through a sequential set of
voltage drops). In another variation, the secondary load 184 is a
resistive load that can function to dissipate residual charge
(e.g., via bleeding off the charge as a current through the
resistive load), which can, in examples, increase switching speed
(e.g., speed of switching the polarity of the output stage).
However, the secondary load 184 can be any other suitable
electrical load.
3.9 System Specific Examples
[0079] In a specific example, the system includes one controller,
one feedback isolator 150, two drive assemblies, and two output
assemblies. The first drive assembly 110 has a first inverter 112
and a first transformer, and the first output assembly 120 has a
first power rectifier; the first output assembly 120 also generates
a positive polarity output sense signal. The second drive assembly
110 has a second inverter 112 and a second transformer, and the
second output assembly 120 includes a second power rectifier; the
second output assembly 120 also generates a negative polarity
output sense signal. The controller 140 receives a voltage
magnitude set point (e.g., from an external source, via a direct
electrical data connection) and, by way of a direct electrical
connection, controls the first and second inverters by way of pulse
width modulated (PWM) voltage signals (e.g., transmitted over
direct electrical connections between the controller 140 and the
inverters) to convert an input direct-current (DC) low power source
170 into a positive polarity (at the first inverter 112 output) and
a negative polarity (at the second inverter 112 output) alternating
current (AC) waveform at low voltage (e.g., having an RMS voltage
magnitude less than one tenth of the desired output voltage
magnitude, less than 1/100.sup.th, 0.1% of the desired output
voltage magnitude, etc.). Parameters of the PWM voltage signals
(e.g., magnitude, duty cycles, frequency, etc.) are determined by
the controller 140 according to the voltage magnitude set point,
based on feedback received (e.g., by way of direct electrical
connection) from the feedback isolator 150. At each drive assembly
110, the low voltage AC waveform is passed through the primary
winding of the first and second transformer, respectively, which
produces a medium voltage (e.g., a factor of 10 greater than the
low voltage, a factor of 2, a factor of 100, a factor of 1000,
etc.) AC waveform across the secondary winding of the first and
second transformer, respectively. In the first drive assembly 110,
which is operated to produce positive polarity high voltage output,
the medium voltage AC waveform is directed (e.g., via direct
electrical connection) from the first transformer 114 to the
positive polarity input of the first power rectifier 122 (e.g., by
a polarity selector 130). In the second drive assembly 110, which
is operated to produce negative polarity high voltage output, the
medium voltage AC waveform is directed (e.g., via direct electrical
connection) from the second transformer 114 to the negative
polarity input of the second power rectifier 122. The medium
voltage AC waveform can be directed to either the positive or
negative polarity input(s) of the power rectifier 122 by a
controllable switch (e.g., a relay) of the polarity selector 130
connected to the controller 140 and connecting the output of the
transformer 114 to either the positive or negative polarity input
of the power rectifier 122 dependent upon the state of the switch,
wherein the controller 140 can actuate the switch in order to
change its state and thereby switch the output polarity of the
associated power rectifier 122. The first power rectifier 122
converts the medium voltage AC waveform to a positive high voltage
DC output (e.g., by way of a series of voltage doubling circuits,
stages, networks, etc.), which can then power a connected load. The
feedback isolator 150 is also directly connected to the output of
the first power rectifier 122 by a first sense pathway, such that a
first output sense signal proportional to the output voltage of the
first power rectifier 122 and of the same polarity (e.g., positive)
is transmitted to and received by the feedback isolator 150. The
second power rectifier 122 converts the medium voltage AC waveform
to a negative high voltage DC output (e.g., by way of a series of
voltage doubling circuits), which can then power a connected load.
The feedback isolator 150 is also directly connected to the output
of the second power rectifier 122 by a second sense pathway, such
that a second output sense signal proportional to the output
voltage of the second power rectifier 122 and of the same polarity
(e.g., negative) is transmitted to and received by the feedback
isolator 150. The feedback isolator 150 generates two feedback
signals: the first feedback signal is generated based on the first
output sense signal (e.g., by amplifying, attenuating, filtering,
transforming, or performing any other suitable signal processing on
the first output sense signal), and the second feedback signal is
generated based on a rectified second output sense signal (e.g.,
based on a positive polarity signal produced upon rectification of
the second output sense signal). The two feedback signals are
provided to the controller 140 (e.g., via direct electrical
connections), which adjusts the output control signals (e.g., the
PWM signals) based on deviation(s) of the feedback signals from the
output voltage set point (e.g., the PWM duty cycle is increased in
order to raise the output voltage when the feedback signals fall
below the output voltage set point, a
proportional-integral-derivative controller 140 is used with the
feedback signals as the inputs and the output control signals as
the outputs, etc.); however, the controller 140 can additionally or
alternatively adjust the output control signals in any suitable
manner to control the output assemblies.
[0080] In another example implementation of the system, as shown in
FIG. 7, a controller, a drive assembly 110, an output assembly 120,
and a feedback isolator 150 are mutually coupled. The controller
140 can generate control signals and provide the control signals to
the drive assembly 110, which provides inverted power to the output
assembly 120, which receives the inverted input power and
transforms the input power into high voltage (HV) output power
(e.g., DC output power). The output assembly 120 also generates
sense signals (e.g., signals encoding data about the output HV
power, such as voltage level, current level, etc.) and provides the
sense signals to the feedback isolator 150. In this example, the
feedback isolator 150 isolates the feedback polarity (e.g.,
rectifies negative polarity feedback to generate positive polarity
feedback, and references the feedback to a different potential upon
output of the feedback versus the reference of the input sense
signals) and generates feedback signals, which the feedback
isolator 150 provides to the controller. The controller 140 can
generate the control signals based on the feedback signals,
external instructions, a combination of feedback signals and
external instructions, or based on any other suitable instructions
or signals.
[0081] In another example implementation of the system, as shown in
FIG. 8, an inverter, a transformer, and a power rectifier 122 are
mutually coupled. The inverter 112 receives low voltage DC input
power and drive signals, and converts the low voltage DC input to a
low voltage AC waveform (e.g., an output) under control of the
drive signals. The transformer 114 transforms the low voltage AC
waveform into a medium voltage AC waveform, and provides current
sense signals (e.g., signals encoding data about the output
current) to an external signal receiver (e.g., a feedback
isolator). The power rectifier 122 converts the medium voltage AC
waveform into a high voltage DC output, and provides voltage sense
signals (e.g., signals encoding data about the output voltage) to
an external signal receiver (e.g., a feedback isolator). The power
rectifier 122 of this example implementation is preferably a
directional power rectifier 122 (e.g., rectifies current flowing in
one direction), but can alternatively be non-directional.
4. Method
[0082] As shown in FIG. 10, the method 200 includes: transforming
an LV DC input into an HV DC output defining an output polarity
S210; powering a load with the HV DC output S220; measuring an
operating parameter of the load S230; and actuating a polarity
selector to switch the output polarity of the HV DC output based on
the operating parameter S240. The method 200 can additionally or
alternatively include: controlling a setpoint of the HV DC output
S222; generating an isolated feedback signal S232; and connecting
two or more reference potentials S234. The method is preferably
performed using the system disclosed above, but can alternatively
be performed using any suitable system.
[0083] Block S210 includes: transforming an LV input into an HV
output defining an output polarity. Block S210 functions to convert
a low voltage input (e.g., input signal) into a high voltage output
(e.g., output signal). The LV input is preferably DC (e.g., from a
battery, an AC-DC converter, a photovoltaic cell, etc.), but can
alternatively be an AC input. The HV output is preferably DC (e.g.,
for application to a load that utilizes DC power), but can
alternatively be AC. Accordingly, the output polarity is preferably
constant (e.g., a positive DC output, a negative DC output, etc.)
until the polarity is switched (e.g., as in Block S240); however,
the output polarity can alternatively be defined instantaneously
for an AC output.
[0084] Block S210 is preferably implemented by a power supply and
components thereof substantially as described above in Section 3;
in particular, Block S210 is preferably implemented by a drive
assembly 110, polarity selector, and output assembly 120
substantially as described above. However, Block S210 can
additionally or alternatively be implemented by and/or in
conjunction with any suitable power supply (e.g., a single-polarity
output power supply, a polarity-selectable power supply, etc.).
[0085] Block S210 can include Block S212, which includes:
converting the LV DC input into an LV alternating current (AC)
output. Block S212 functions to transform the DC input signal into
a form that can be stepped up in voltage by a transformer, which
operates on an AC input. Block S212 is thus preferably implemented
using an inverter that converts a DC input to an AC output. The
inverter is preferably an inverter substantially as described above
in Section 3 (e.g., a half bridge MOSFET inverter, a full bridge
MOSFET inverter, etc.), but can additionally or alternatively be
any suitable inverter or other mechanism for conversion of DC input
to AC output.
[0086] Block S210 can include Block S214, which includes:
converting the LV AC output into a medium voltage (MV) AC output.
Block S214 functions to step the voltage of the LV AC output (e.g.,
the peak-to-peak voltage, the RMS voltage magnitude, etc.) up to a
higher value while retaining the AC character of the output. Thus,
Block S214 is preferably implemented at a step-up transformer
substantially as described above in Section 3; however, Block S214
can additionally or alternatively be implemented using any suitable
mechanism for increasing the voltage of an AC input.
[0087] Block S210 can include Block S216, which includes:
converting the MV AC output into the HV DC output. Block S216
functions to simultaneously increase the voltage of an MV AC signal
(e.g., received as an input) to a higher voltage level and convert
the MV AC signal to a direct current output (e.g., the HV DC
output). Block S216 is preferably implemented at a power rectifier
that includes a voltage ladder substantially as described above in
Section 3; however, Block S216 can additionally or alternatively be
implemented using any suitable mechanism for increasing the voltage
of an AC input signal and converting the AC input signal to a DC
output (e.g., a second step-up transformer coupled with a full-wave
rectifier, half-wave rectifier, and any other suitable rectifier
combined with a component that steps up voltage). The output
polarity is preferably defined by the state of a polarity selector
connected between a transformer (e.g., as implemented in variations
of Block S214) and a power rectifier used in variations of Block
S216, but can be otherwise suitably defined (e.g., by selecting the
polarity of the LV DC input, by selecting the polarity of the HV DC
output downstream of the power rectifier or other output,
etc.).
[0088] In a specific example, Block S210 includes: at a power
supply, transforming a first low voltage (LV) direct current (DC)
input into a first HV DC output defining an output polarity
relative to an HV reference potential, wherein the output polarity
is one of a first polarity and a second polarity opposite the first
polarity, wherein transforming includes converting the first LV DC
input into a first LV alternating current (AC) output at an
inverter of the power supply, converting the first LV AC output
into a first medium voltage (MV) AC output at a step-up transformer
of the power supply, and converting the first MV AC output into the
first HV DC output at a power rectifier of the power supply.
[0089] Block S220 includes: powering a load with the HV DC output.
Block S220 functions to perform electrical work using the HV DC
output (e.g., as generated in Block S210). The load can include any
suitable load that utilizes high voltage direct current power,
including any load substantially as described above in Section 3
(e.g., an ion thruster, a colloid-fueled ion electrospray thruster,
an ion source, an ion emitter, an electrostatic particulate
scrubber, an extractor grid, an acceleration grid, etc.). However,
Block S220 can additionally or alternatively include powering any
suitable load in any suitable manner.
[0090] In a specific example, Block S220 includes powering an
emitter of the ion emitter with the HV DC output. In this example,
the ion emitter emits ions having an ion polarity equal to the
output polarity of the HV DC output (e.g., generated in Block
S210), because powering the ion emitter in this example includes
charging the emitter (e.g., vs an extractor) of an electrostatic
ion emitter at the HV potential, and extracting opposing-polarity
ions from the emitter based on the relative potential between the
emitter charged to the HV potential relative to the extractor.
[0091] In another specific example, Block S220 includes powering an
extractor of the ion emitter with the HV DC output. In this
example, the ion emitter emits ions having an ion polarity opposite
the output polarity of the HV DC output (e.g., generated in Block
S210), because powering the ion emitter in this example includes
charging an extractor of an electrostatic ion emitter at the HV
potential, and extracting opposing-polarity ions from an emitter
using the extractor charged to the HV potential.
[0092] The method can include Block S222, which includes:
controlling a setpoint of the HV DC output. Block S222 functions to
maintain an output characteristic of the HV DC output using a
controller. The output characteristic controlled in relation to
Block S222 can include: an output voltage, a maximum current drawn
by a load, an output current, a maximum voltage ripple, a maximum
current ripple, a duration of continuous operation, a duration of
continuous operation at a single output polarity, a duration of
total operation at a single output polarity, and any other suitable
output characteristic. The setpoint controlled in accordance with
Block S222 can be, in examples, a voltage setpoint, a current
setpoint, and any other suitable setpoint. Block S222 is preferably
implemented using a controller 140 and/or components thereof (e.g.,
a PWM controller 148, a microcontroller) substantially as described
above in Section 3; however, Block S222 can additionally or
alternatively be implemented using any suitable control system or
module.
[0093] Block S222 can include controlling a plurality of setpoints
associated with multiple HV DC outputs and/or loads. Controlling
the plurality of setpoints can, in variations, be based on a
desired overall load output characteristic such as a thrust vector
(e.g., the net thrust produced by a plurality of ion thrusters), a
desired accumulated charge imbalance (e.g., a zero charge
imbalance, a positive charge imbalance, a charge imbalance based on
an environmental charge, etc.), and any other suitable
characteristic. For example, in cases wherein a first and second
ion emitter drawing a first and second ion current, respectively,
are used, Block S222 can include controlling, at a controller, a
first magnitude of the first HV DC output and a second magnitude of
the second HV DC output such that the first ion current is greater
than the second ion current (e.g., to provide a net positive or
negative ion current, to produce a net thrust, etc.). For example,
Block S222 can include measuring an environmental charge (e.g., a
local charge in the environment around the system), and controlling
relative magnitude of the first and second HV DC outputs to
generate an accumulated charge imbalance at the system that negates
(e.g., opposes in an equal and opposite manner) the environmental
charge. However, Block S222 can additionally or alternatively
include controlling a plurality of setpoints in any other suitable
manner.
[0094] Block S230 includes: measuring an operating parameter of the
load. Block S230 functions to automatically determine one or more
parameters related to load operation while the load is under power
(e.g., by way of the HV DC output). The operating parameter can
include the output characteristic for which a setpoint is
controlled in conjunction with Block S222 (e.g., an output voltage,
current draw, etc.). However, the operating parameter may not
necessarily include or be represented solely by the output
characteristic controlled in relation to Block S222. Block S230 can
be performed by and/or in conjunction with various sensors,
including a sense signal input of a feedback isolator 150
substantially as described above in Section 3, and/or a space
charge sensor (e.g., a potential probe, a Langmuir probe, a
conducting surface attached to a voltage transducer, a charge
counter, etc.), a thrust sensor (e.g., a thrust balance), a
flowrate monitor (e.g., a propellant flow meter, an ion flowrate
monitor, etc.), a pressure sensor (e.g., a propellant tank vapor
pressure monitor), a current monitor (e.g., to measure ion current
drawn by the load), a temperature sensor (e.g., a thermocouple to
monitor thruster temperature, a thermistor to monitor power supply
component temperatures, etc.), and any other suitable sensors.
Sensor outputs can be processed by a controller substantially as
described above in Section 3 in variations of Block S230. However,
Block S230 can additionally or alternatively include measuring an
operating parameter of the load in any other suitable manner.
[0095] In relation to Block S230, an operating parameter can
include various parameters relevant to load operation. For example,
the operating parameter can include: current drawn by the load,
voltage applied to the load, thrust produced by the load, space
charge generated by the load (e.g., as a result of ion emission),
parasitic current drawn by a portion of the load, temperature of
the load, load status (e.g., a qualitative status such as `nominal`
vs. `off-nominal` operation, a quantitative status such as a
percentage of maximum allowable current being drawn, etc.), and any
other suitable parameter. The operating parameter can additionally
or alternatively include any parameter and/or variable described
above in Section 3 in relation to a primary load 182, a secondary
load 184, and any other suitable load.
[0096] In a specific example, Block S230 includes measuring, at a
controller of the power supply, an operating parameter of an ion
emitter. However, Block S2230 can additionally or alternatively
include otherwise suitably measuring any suitable operating
parameter of any suitable load.
[0097] The method can include Block S232, which includes:
generating an isolated feedback signal. Block S232 functions to
detect a sense signal from a high voltage output (e.g., the HV DC
output), which is referenced to a first reference potential (e.g.,
an HV reference potential), and produce a feedback signal that is
proportional to the sense signal value but is referenced to a
second reference potential (e.g., an LV reference potential). Block
S232 is preferably performed using a feedback isolator
substantially as described above in Section 3, but can additionally
or alternatively be performed using any other suitable isolation
mechanism that electrically decouples (e.g., isolates) the
reference potentials between two or more signals (e.g., a third
winding of the transformer).
[0098] The method can additionally or alternatively include
generating a feedback signal, wherein the feedback signal is not
isolated. For example, the feedback signal can be referenced to the
first reference potential (e.g., the same reference potential as
that of the sense signal and various other portions of the system).
However, the method can include generating feedback signals that
are isolated or non-isolated in any other suitable manner.
[0099] The method can include Block S234, which includes:
connecting two or more reference potentials. Block S234 functions
to equalize the reference potentials of two or more signals. Block
S234 can also function to pull a virtual ground (e.g., to which the
HV output is referenced) to a chassis ground (e.g., to which a
control signal or feedback signal is referenced) to affect an
output characteristic of the output assembly 120 (e.g., the output
voltage, the maximum allowed output current, etc.). Block S234 can
also function to selectively switch control of the output power
(e.g., of the power supply) from an analog or passive
charge-balancing mode to a digital or active charge-balancing mode,
wherein a controller can actively control charge balancing (e.g.,
by computing and controlling the drive assemblies based on output
feedback instead of a closed feedback loop using analog or passive
control). Block S234 is preferably performed using a crowbar switch
substantially as described above in Section 3, but can additionally
or alternatively be performed using any suitable
electrical-connection mechanism or switch.
[0100] Block S240 includes: actuating a polarity selector to switch
the output polarity of the HV DC output. Block S240 functions to
change the output polarity of the HV DC output between positive and
negative polarity. Block S240 is preferably performed based on an
operating parameter (e.g., a value of the measured operating
parameter in variations of Block S230), but can additionally or
alternatively have any suitable basis. For example, Block S240 can
include actuating the polarity selector based on an accumulated
charge imbalance measured at a space charge sensor, wherein an
accumulated charge imbalance of a threshold charge value triggers
actuation of the polarity selector and emission of ions of a
suitable polarity to negate the accumulated charge imbalance. In
another example, Block S240 can include actuating the polarity
selector to selectively build up space charge, wherein the
magnitude and polarity of the space charge can be determined based
on the operation environment (e.g., wherein the operation
environment removes space charge of a given polarity at a given
rate, as determined from the operating parameter; wherein the
operation environment is associated with a target space charge
magnitude and polarity; etc.). In another example, Block S240
includes actuating the polarity selector based on an elapsed time,
wherein after a predetermined elapsed time the output polarity is
switched (e.g., periodically). However, Block S240 can have any
other suitable basis.
[0101] Block S240 is preferably performed subsequent to Block S214
and prior to Block S216 (e.g., by a polarity selector arranged
between the secondary stage of the step up transformer and the
input stage of the power rectifier). However, Block S240 can
alternatively be performed after power rectification to a HV DC
output, prior to inversion at the LV AC output, and at any other
suitable location (or time point) in the input-output
transformation chain (e.g., between the LV DC input and the HV DC
output).
[0102] In a specific example, Block S240 includes actuating a
polarity selector of the power supply, using a controller of the
power supply, based on a measured operating parameter. In this
example, actuating the polarity selector is performed
simultaneously with powering the load (e.g., an ion emitter),
without cessation of power to the load (e.g., operating the load
continuously while switching the polarity). In this example, the
polarity selector is arranged between a step-up transformer and a
power rectifier of the power supply, actuating the polarity
selector switches the output polarity between the first polarity
and the second polarity.
[0103] In a related example of Block S240, the operating parameter
includes an ion current emitted by an ion emitter, and actuating
the polarity selector is performed at an actuation frequency. The
actuation frequency in this example has an actuation period, and
the actuation frequency is determined (e.g., by the controller and
based on the measured ion current) in order to maintain the net
current at zero (e.g., a net sum of ion currents associated with
positive ions and negative ions over the period is equal to zero,
such that little to no space charge is generate). Note that the
relationship between actuation frequency and actuation period is
preferably the period of time over which a full cycle of actuation
has occurred (e.g., from positive, to negative, and back to
positive); however, the actuation period can be otherwise suitably
defined (e.g., as the inverse of the actuation frequency). In a
specific example, the actuation frequency is 0.1 Hz (e.g., the
polarity is switched every 10 seconds), and the actuation period in
this example is 20 seconds (e.g., wherein a full cycle of both a
first polarity and second polarity are experienced at the high
voltage output). However, the actuation frequency and period can be
otherwise suitably related.
[0104] In a related example of Block S240, the operating parameter
includes an accumulated charge imbalance associated with an ion
emitter (e.g., emitting ions of a single polarity over a period of
time), and Block S240 includes switching the output polarity based
on the accumulated charge imbalance exceeding a threshold value
(e.g., the charge value exceeding a threshold charge value, the
voltage difference between the spacecraft potential and a reference
potential, etc.).
[0105] In another example, Block S240 includes maintaining two
output polarities (e.g., associated with two output assemblies of a
power supply) in opposition during actuation. In this example,
Block S240 includes maintaining the first output polarity and the
second output polarity as opposing polarities. This example can
include maintaining a first ion current drawn by a first ion
emitter substantially equal to and opposite in polarity to a second
ion current drawn by a second ion emitter; however, this example
can additionally or alternatively include maintaining the voltage
of the HV DC outputs at opposite polarities. This example of Block
S240 can be implemented in conjunction with variations of Block
S222, wherein the output value (e.g., voltage level) is maintained
(e.g., at a setpoint) in accordance with Block S222 and the
polarities are maintained in accordance with Block S240.
[0106] The method 200 and Blocks thereof can additionally or
alternatively include performing any suitable action in relation to
the function(s) as described above with regard to the system loo,
components of the system 100, and/or similar systems and
components.
[0107] Although omitted for conciseness, the embodiments include
every combination and permutation of the various system components
and the various method processes, including any variations,
examples, and specific examples, where the method processes can be
performed in any suitable order, sequentially or concurrently using
any suitable system components.
[0108] The system and method and embodiments thereof can be
embodied and/or implemented at least in part as a machine
configured to receive a computer-readable medium storing
computer-readable instructions. The instructions are preferably
executed by computer-executable components preferably integrated
with the system. The computer-readable medium can be stored on any
suitable computer-readable media such as RAMs, ROMs, flash memory,
EEPROMs, optical devices (CD or DVD), hard drives, floppy drives,
or any suitable device. The computer-executable component is
preferably a general or application specific processor, but any
suitable dedicated hardware or hardware/firmware combination device
can alternatively or additionally execute the instructions.
[0109] As a person skilled in the art will recognize from the
previous detailed description and from the figures and claims,
modifications and changes can be made to the preferred embodiments
of the invention without departing from the scope of this invention
defined in the following claims.
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